• Nuclear Engineering and Technology
• /
• v.43 no.4
• /
• pp.361-374
• /
• 2011

Two types of numerical modeling techniques were considered for the dynamic response of a structure subjected to a ground acceleration. One technique is based on the equation of motion relative to ground motion, and the other is based on the equation of absolute motion of the structure and the ground. The analytic background of the former is well established while the latter has not yet been extensively verified. The latter is called a large mass method, which allocates an appropriate large mass to the ground so that it causes the ground to move according to a given acceleration time history. In this paper, through the use of a single degree-of-freedom spring-mass system, the equations of motion of the two techniques were analyzed and useful theorems are provided on the large mass method. Using simple examples, the numerical results of the two modeling techniques were compared with analytic solutions. It is shown that the theorems provide a clear insight on the large mass method.

• Journal of Cerebrovascular and Endovascular Neurosurgery
• /
• v.25 no.2
• /
• pp.208-213
• /
• 2023

Flow-diverting stents (FDSs) have proven advantageous for the treatment of large, fusiform, and dissecting aneurysms that are otherwise difficult to treat. Retreatment strategies for recurrent large or giant aneurysms after FDSs are limited to overlapping implantation of an additional FDS or definitive occlusion of the parent vessel. We report a recurrent giant aneurysm that was initially treated with an FDS with coils and was successfully treated with an additional FDS. Visual symptoms due to the mass effect of the recurrent aneurysm were completely resolved, and follow-up digital subtraction angiography revealed complete obliteration of the aneurysm. Additional FDS implantation for the retreatment of incompletely occluded aneurysms after the initial FDS treatment may be feasible and safe. Further studies are required to validate these results.

• Journal of The Korean Astronomical Society
• /
• v.46 no.1
• /
• pp.41-47
• /
• 2013

I present a simple scheme for the treatment of gravitational interactions on galactic scales. In anal- ogy with known mechanisms of quantum field theory, I assume ad hoc that gravitation is mediated by virtual exchange particles-gravitons-with very small but non-zero masses. The resulting den- sity and mass profiles are proportional to the mass of the gravitating body. The mass profile scales with the centripetal acceleration experienced by a test particle orbiting the central mass, but this comes at the cost of postulating a universal characteristic acceleration $a_0{\approx}4.3{\times}10^{-12}msec^{-2}$ (or $8{\pi}a_0{\approx}1.1{\times}10^{-10}msec^{-2}$). The scheme predicts the asymptotic flattening of galactic rotation curves, the Tully-Fisher/Faber-Jackson relations, the mass discrepancy-acceleration relation of galaxies, the surface brightness-acceleration relation of galaxies, the kinematics of galaxy clusters, and "Renzo's rule" correctly; additional (dark) mass components are not required. Given that it is based on various ad-hoc assumptions and given further limitations, the scheme I present is not yet a consistent theory of gravitation; rather, it is a "toy model" providing a convenient scaling law that simplifies the description of gravity on galactic scales.

• Structural Engineering and Mechanics
• /
• v.63 no.4
• /
• pp.537-549
• /
• 2017

One of the main concerns of civil engineering researchers is developing or modifying an energy dissipation system that can effectively control structural vibrations, and keep the structural response within tolerable limits during unpredictable events like earthquakes, wind and any kind of thrust load. This article proposes a new type of mass damper system for controlling wideband earthquake vibrations, called Multiple Wall Dampers (MWD). The basic principle of the Tuned Mass Damper (TMD) was used to design the proposed wall damper system. This passive energy dissipation system does not require additional mass for the damping system because the boundary wall mass of the building was used as a damper mass. The multi-mode approach was applied to determine the location and design parameters of the dampers. The dampers were installed based on the maximum amplitude of modes. To optimize the damper parameters, the multi-objective optimization Response Surface Methodology was used, with frequency response and maximum displacement as the objective functions. The obtained structural responses under different earthquake forces demonstrated that the MWD is one of the most capable tools for reducing the responses of multi-storied buildings, and this system can be practically used for new and existing building structures.

• Journal of Veterinary Clinics
• /
• v.32 no.1
• /
• pp.115-119
• /
• 2015

An 11-year-old spayed female maltese was presented for abdominal distention, dysuria and dyschezia. Panting and heart murmur was found and abdominal palpation was difficult due to increased abdominal pressure. A soft tissue mass, $6{\times}3cm$ in size, was identified radiographically in pelvic canal, displacing the descending colon to the medioventral direction and the urinary bladder cranially. On ultrasonography, the mass consisted of homogeneous hypoechoic parenchyma containing the focal hyperechoic region ($1.6{\times}1.5cm$). The mass had distinct margin and no connection with adjacent organs. It was considered as a mass originating from the retroperitoneal cavity. Additional diagnostic procedures were not advanced because of the owner's request, and only a surgical excision of the mass was performed to alleviate the dysuria and dyschezia. Histopathologic examination and immunohistochemistry determined the mass as a soft tissue sarcoma and excluded hemangiosarcoma and osteosarcoma, both are the most common types of the retroperitoneal tumors. This report described non-vascular soft tissue sarcoma originating from the retroperitoneal cavity in a maltese dog.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2004.11a
• /
• pp.271-276
• /
• 2004

In this paper. dynamic behavior of the cracked beam under a moving mass is presented using the finite element method (FEM). Model accuracy is improved with the following consideration: (1) FE model with Timoshenko beam element (2) Additional flexibility matrix due to crack presence (3) Interaction forces between the moving mass and supported beam. The Timoshenko bean model with a two-node finite element is constructed based on Guyan condensation that leads to the results of classical formulations. but in a simple and systematic manner. The cracked section is represented by local flexibility matrix connecting two unchanged beam segments and the crack as modeled a massless rotational spring. The inertia force due to the moving mass is also involved with gravity force equivalent to a moving load. The numerical tests for various mass levels. crack sizes. locations and boundary conditions were performed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.159-163
• /
• 2005

A dynamic vibration absorber using the Zener's model has been taken into account with respect to frequency response characteristics. The concept of the tuned mass damper with a single degree of freedom has been well applied for many industrial fields, because many researchers have extensively studied various basic characteristics, performance and optimization methods for long time. The Zener's model has an additional spring, which is connected between a damper and a mass, while the tuned mass damper with a single degree of freedom consists of a mass, a spring and a damper connected in parallel. In previous works, the basic performance and characteristics of the Zoner's model as a dynamic vibration absorber have not been investigated. In this study, the frequency response characteristics according to the parameter change of the Zener's model have been described. In order to find the optimum value of several parameters, we use iterative scheme with three dimensional frequency response diagram by MATLAB programming. Present results shows the Zener's model can give more good damping performance than the simple tuned mass damper, and the numerical of optimization method should be developed for the efficient vibration absorbtion.

• The Journal of the Acoustical Society of Korea
• /
• v.29 no.7
• /
• pp.439-447
• /
• 2010

In this paper, the resonant characteristic of a Tonpilz transducer with a fixed tail mass has been researched and the feasibility to utilize the transducer in that resonant frequency has been analyzed. The additional resonance is occurred by adhering an elastic tube to the tail mass of a conventional Tonpilz transducer and fixing the other end of the tube. The characteristic of this low resonant mode is analyzed by means of the finite element method, then it is shown that this mode is affected by the variation of the stiffness of the tube as well as the mass of the head mass and tail mass. Based on the analysis results, the Tonpilz transducer is designed to meet specific performance conditions.

• Journal of Nutrition and Health
• /
• v.28 no.11
• /
• pp.1049-1055
• /
• 1995

This study was designed to investigate the effects of calcium supplementation on calcium metabolism in seven healthy college women, aged from 19 to 21 years old. For this purpose, metabolic studies were conducted for two weeks. During the first week, the subjects ate experimental diet which nutrients composition was similar to their usual intake. And during the consecutive second week, they ate the same experimental diet supplemented with 500mg of calcium daily. The results were summarized as follows ; 1) Fecal excretion of calcium increased significantly (P<0.05), but urinary excretion of that did not show any change after supplementary intake of calcium. 2) Mean apparent calcium absorption was 28.5% and retention was 182mg/day when subjects ate the experimental diet without calcium supplementation. Calcium retention was significantly ate the experimental diet without calcium supplementation. Calcium retention was decreased to 24.1% by additional intake of calcium. 3) Phosphorus balance did not show any change after additional intake of calcium. 4) Serum calcium level was also not changed by additional intake of calcium. 5) Serum calcium level increased significantly(P<0.05) but serum phosphorus level did not show any change after additional intake of calcium. The above results showed that supplementation of 500mg calcium daily can be helpful to increase calcium retention as well as the peak bone mass in young women eating usual Korean diets.

• Smart Structures and Systems
• /
• v.19 no.6
• /
• pp.665-678
• /
• 2017

In this paper the tuned mass-damper-inerter (TMDI) is considered for passive vibration control and energy harvesting in harmonically excited structures. The TMDI couples the classical tuned mass-damper (TMD) with a grounded inerter: a two-terminal linear device resisting the relative acceleration of its terminals by a constant of proportionality termed inertance. In this manner, the TMD is endowed with additional inertia, beyond the one offered by the attached mass, without any substantial increase to the overall weight. Closed-form analytical expressions for optimal TMDI parameters, stiffness and damping, given attached mass and inertance are derived by application of Den Hartog's tuning approach to suppress the response amplitude of force and base-acceleration excited single-degree-of-freedom structures. It is analytically shown that the TMDI is more effective from a same mass/weight TMD to suppress vibrations close to the natural frequency of the uncontrolled structure, while it is more robust to detuning effects. Moreover, it is shown that the mass amplification effect of the inerter achieves significant weight reduction for a target/predefined level of vibration suppression in a performance-based oriented design approach compared to the classical TMD. Lastly, the potential of using the TMDI for energy harvesting is explored by substituting the dissipative damper with an electromagnetic motor and assuming that the inertance can vary through the use of a flywheel-based inerter device. It is analytically shown that by reducing the inertance, treated as a mass/inertia-related design parameter not considered in conventional TMD-based energy harvesters, the available power for electric generation increases for fixed attached mass/weight, electromechanical damping, and stiffness properties.